Off the deep end

GlobalData analyst Gregory Bosunga takes a look at the ten most challenging pipelay jobs around the world.

McDermott subsea construction vessel NO102 installed umbilicals totaling 65mi with other related subsea structures for Jack/St. Malo. Image from McDermott International.

The most challenging pipelay projects are located in the ultra-deep waters of the Gulf of Mexico and Brazil, where fields can range from 1524m (5000ft) to 2956m (9700ft), such as Perdido in the Gulf of Mexico. Distances to shore can also reach 380km (230mi), such as the Cabiúnas field in Brazil.

Additionally, the seabed surface of pipeline routes to existing networks can be extremely irregular, meaning that geophysical surveys have become increasingly important as a means of identifying areas where significant lengths of unsupported pipeline must be minimized in order to avoid pipeline failures. Some of the engineering challenges involved in laying the pipelines are related to high hydrostatic pressures, cold temperatures, and darkness. The selected route must also avoid obstructing the infrastructure of existing facilities and comply with regulations aimed at minimizing the negative impact on the subsea environment.

Most of the ultra-deep pipelines are laid using the J-lay method. The traditional method for installing offshore pipelines in relatively shallow waters is commonly referred to as the S-lay method, named because the profile of the pipe as it moves in a horizontal plane from the welding and inspection stations on the lay barge, across the stern of the lay barge, and onto the ocean floor forms an elongated “S.” A comparatively new method for installing offshore pipelines in deeper waters is the J-lay method, so-called because the configuration of the pipe as it is being assembled resembles a “J.” Most of the ultra-deep pipelines are laid using the J-lay method, which is more costly and technically challenging than the S-lay method.

The 12 most challenging pipeline projects

Gregory Bosunga is analyst, Americas onshore upstream research for GlobalData. Gregory has a M.S. in mineral economics from Colorado School of Mines and an MBA and a Master of Project Management from the Keller Graduate School of Management.